Sudden loss of oil pressure...
07-17-2009, 03:52 AM
#1
Sudden loss of oil pressure... We just got my buddy's '97 z28 back on the road. Lower mileage block, new CC502 cam, full bolt on's, stock stalled A4, 3.42 10 bolt.
Things were going great, just hooked up the wiring for the ewp. Started it up for the first time and let it reach operating temp. Car idled and ran very well. Oil pressure was strong so we took it for a test drive on the freeway.
My buddy went WOT on the freeway at around 60mph, he said at ~90mph the car just shut off. he coasted to the side of the freeway. The car didn't want to restart at first, sounded like the starter grinding. Finally it restarted after a few mins but the oil pressure is at zero now. It will rise a little when you give it rpm, but as soon as you let off the gas, it drops immediately to zero. No knocks, ticks, nothing. Car starts and runs fine, but nada for oil pressure, so we can't run it for long. I am going to troubleshoot this weekend.
I am going to hook up a mechanical gauge, but assuming that the sensor is not the problem, what could it be? Pick up tube fell off?
Things were going great, just hooked up the wiring for the ewp. Started it up for the first time and let it reach operating temp. Car idled and ran very well. Oil pressure was strong so we took it for a test drive on the freeway.
My buddy went WOT on the freeway at around 60mph, he said at ~90mph the car just shut off. he coasted to the side of the freeway. The car didn't want to restart at first, sounded like the starter grinding. Finally it restarted after a few mins but the oil pressure is at zero now. It will rise a little when you give it rpm, but as soon as you let off the gas, it drops immediately to zero. No knocks, ticks, nothing. Car starts and runs fine, but nada for oil pressure, so we can't run it for long. I am going to troubleshoot this weekend.
I am going to hook up a mechanical gauge, but assuming that the sensor is not the problem, what could it be? Pick up tube fell off?
07-17-2009, 09:09 AM
#3
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Usually the symptoms for an oil p/u falling off is low oil pressure when braking. I would first start looking at the oil pump drive gear and shaft. If those are fine then I would only assume bearings have given up. You can tap on the bottom of the pan to see if the p/u is off and bouncing around...
07-17-2009, 11:35 AM
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We just got my buddy's '97 z28 back on the road. Lower mileage block, new CC502 cam, full bolt on's, stock stalled A4, 3.42 10 bolt.
Things were going great, just hooked up the wiring for the ewp. Started it up for the first time and let it reach operating temp. Car idled and ran very well. Oil pressure was strong so we took it for a test drive on the freeway.
My buddy went WOT on the freeway at around 60mph, he said at ~90mph the car just shut off. he coasted to the side of the freeway. The car didn't want to restart at first, sounded like the starter grinding. Finally it restarted after a few mins but the oil pressure is at zero now. It will rise a little when you give it rpm, but as soon as you let off the gas, it drops immediately to zero. No knocks, ticks, nothing. Car starts and runs fine, but nada for oil pressure, so we can't run it for long. I am going to troubleshoot this weekend.
I am going to hook up a mechanical gauge, but assuming that the sensor is not the problem, what could it be? Pick up tube fell off?
Things were going great, just hooked up the wiring for the ewp. Started it up for the first time and let it reach operating temp. Car idled and ran very well. Oil pressure was strong so we took it for a test drive on the freeway.
My buddy went WOT on the freeway at around 60mph, he said at ~90mph the car just shut off. he coasted to the side of the freeway. The car didn't want to restart at first, sounded like the starter grinding. Finally it restarted after a few mins but the oil pressure is at zero now. It will rise a little when you give it rpm, but as soon as you let off the gas, it drops immediately to zero. No knocks, ticks, nothing. Car starts and runs fine, but nada for oil pressure, so we can't run it for long. I am going to troubleshoot this weekend.
I am going to hook up a mechanical gauge, but assuming that the sensor is not the problem, what could it be? Pick up tube fell off?
cars dont just shut off when a pick up tube falls off but i guess my theory doesnt really explain the hard to start and the grindind either 
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07-17-2009, 11:47 AM
#8
doesnt sound like pick up tube problems to me sounds... like a spun cam bearing from one getting nocked around when installing the cam. now its blocking a oil passsage cars dont just shut off when a pick up tube falls off but i guess my theory doesnt really explain the hard to start and the grindind either
cars dont just shut off when a pick up tube falls off but i guess my theory doesnt really explain the hard to start and the grindind either
07-17-2009, 01:19 PM
#9
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eeeeww well then who knows what the guy could have done to it...
id do as you said and try to figure out simple things before i go digging into the internals of the engine hopefully it stops there and its someting dumb and not totally f'd up
id do as you said and try to figure out simple things before i go digging into the internals of the engine hopefully it stops there and its someting dumb and not totally f'd up
07-18-2009, 10:25 AM
#11
Hydraulic rollers? First sign of really low, or no oil pressure is clattering lifters. If it seems to be running OK, and the lifters aren't clattering, I'd suspect the oil pressure sensor. Any chance that it's wired into the PCM to kill the engine if the oil pressure goes below a certain point?
Sometimes cars do weird things....I used to have a '77 Pontiac T/A. I was out crusing for about an hour one night, nothing crazy of fast, just easy cruising. I get about 500 yards from home, all of a sudden the car starts running rough, and I start to hear engines noises. I look at the oil pressure gauge, and it's almost bottomed out.
I dump in the clutch, kill the ignition, and barely manage to coast into my driveway. I pushed the car by hand back to the garage, but couldn't get it inside, due to the rise of the driveway.
I pull the dipstick, it's full. WTF???
By now it's a little late to start tearing into things, fortunately I had the DD to drive to work the next day. I get home from work, jack up the car, pull the oil filter and cut it open....nothing nasty. OK, now what? I get a new oil filter, fill it up with fresh oil, disconnect the coil wire, spin the engine for a few seconds, the oil pressure gauge starts to rise. Hook the coil back up, start the engine, the gauge flutters for a few seconds, and jumps to 40 lbs. Within another few seconds, the lifters all pumped back up, and the car ran fine for another 9-10 years. I NEVER figured out what happened....
Sometimes cars do weird things....I used to have a '77 Pontiac T/A. I was out crusing for about an hour one night, nothing crazy of fast, just easy cruising. I get about 500 yards from home, all of a sudden the car starts running rough, and I start to hear engines noises. I look at the oil pressure gauge, and it's almost bottomed out.
I dump in the clutch, kill the ignition, and barely manage to coast into my driveway. I pushed the car by hand back to the garage, but couldn't get it inside, due to the rise of the driveway.
I pull the dipstick, it's full. WTF???
By now it's a little late to start tearing into things, fortunately I had the DD to drive to work the next day. I get home from work, jack up the car, pull the oil filter and cut it open....nothing nasty. OK, now what? I get a new oil filter, fill it up with fresh oil, disconnect the coil wire, spin the engine for a few seconds, the oil pressure gauge starts to rise. Hook the coil back up, start the engine, the gauge flutters for a few seconds, and jumps to 40 lbs. Within another few seconds, the lifters all pumped back up, and the car ran fine for another 9-10 years. I NEVER figured out what happened....
08-09-2009, 01:07 PM
#13
I would think the cam bearings are gone if there is no knock.Drop the pan and see how many chunks you find.Could be the drive gear also but then you would not have any press.So pull the intake too,whatever it is you can bet the all of the bearings are shot and the pistons/bores are probably scored as well.
08-09-2009, 01:13 PM
#14
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Cold idle psi means nothing, the oil is much thicker and can "hide" problems such as spun bearings. Let it get hot, I mean 30+ mins of driving (if you can of course) then that is when should get and accurate hot idle psi. If its a bad cam bearing it will cause low pressure mainly at idle and hot. Cold it'll be ok, but once hot its real low. Rod bearings seem to be low everywhere, especially at high rpm's.
Let us know what you find out.
Let us know what you find out.
08-09-2009, 06:24 PM
#15
Well we let it warm up and oil pressure dropped to zero again. Drained the oil and it was pretty silver. So we already tore open the engine bay for a LQ4 swap. We haven't disected the bottom end yet, but I will to find out exactly what went wrong.
08-09-2009, 07:56 PM
#16
damn that fkn sucks well atleast you have a swap motor laying around now....and yes typically low oil psi indicates a bad cam bearing but when you give it gas just off idle and its fine....cam bearings, but if it has oil pressure at high rpms or anything above idle thats all that counts.lol
08-10-2009, 01:41 PM
#17
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Damn that blows, was this Alex's ride?
I'm having the same low oil pressure problems, usually when I only come to a hard stop it goes down to 5 and my car turns off..showing the "check gauges"
I'm having the same low oil pressure problems, usually when I only come to a hard stop it goes down to 5 and my car turns off..showing the "check gauges"
